We are studying the social influences on reproductive suppression and reproductive maturation in Callitrichid monkeys. We have developed and validated several urinary hormonal assays that correlate well with serum values. We can use these noninvasive techniques to monitor reproductive hormones in freely moving monkeys. We will extend these techniques to fecal assays and to urinary testosterone and prolactin assays. These assays will then be used in several behavioral studies. To examine how reproductive females inhibit ovulation in subordinate females we will present females removed form family groups and housed adjacent to novel males with scent marks or urine from their mothers or from novel females in comparison with controls to see if either marks or urine can delay ovulation. The onset of ovulation appears to require visual, auditory and airborne olfactory stimulation from a novel male, and the role of these stimuli will be examined further. Estrone and LH values drop in pre- reproductive females upon the birth of new infants in the group. Behavioral and hormonal observations from prior to birth through the period when infants are carried by other family members will examine the mechanism of this additional suppression. Although females living with a reproductive female do not ovulate, some hormonal activity appears related to dominance. When the dominant daughter is removed from a group, we follow the hormonal and behavioral changes in the remaining daughters to see if we can predict which female will show increased hormonal activity. Comparative data indicate that marmosets have different mechanisms of suppression from tamarins. We will study mechanisms of suppression in pygmy marmosets to see if daughters ovulate while with their mothers. Little attention has been given to male reproductive development in tamarins. We will use the testosterone assay in combination with behavioral observations to see if suppression of sexual behavior in subordinate males is physiological, behavioral, or a combination of both. Finally, we examine the role of prolactin in promoting communal infant care. Are changes in prolactin levels a cause or a consequence of infant care? These studies taken together will increase our understanding of the ontogeny of reproductive behavior and of the variety of social influences on reproduction in marmosets and tamarins.